DOT is the text file format of the suite GraphViz. It has a human-readable syntax that describes network data, including subgraphs and elements appearances (i.e. color, width, label). NetworkX, Tulip or ZGRViewer can import DOT files as well. Additional informations can be found on Wikipedia.

The following link shows the official website, where information is available about the DOT format.

Gephi currently doesn’t provide a complete support of the DOT format. Subgraphs are not supported, nor custom attributes or size. Only labels and colors are imported if present. Directed and undirected graphs are supported.